Effect of the most severe summer-autumn droughts on the yield of winter wheat on different precursors in the arid conditions of the Eastern Caucasus

   Relevance. To study regularities of severe droughts influence and to develop measures on decreasing their negative consequences on crop capacity are important tasks of arable farming.
   Methods. A long-term experiment was laid in the Prikumskaya experimental station in 1969. The research was conducted in the 6-field grain and fallow crop rotation in the years with HC 0,12–0,30 in July – October.
   The aim of the research was to study the effect of the most severe droughts of the summer-autumn period on the moisture supply, growth, development and yield of winter wheat on background of bare fallow and semi-fallow in the arid zone of Stavropol Territory.
   Results. The reserves of productive moisture in the 1 m layer of soil in autumn for sowing on background of bare fallow in 4, semi-fallow – in 5 out of 7 years were below the norm, and in 3 years on non-fallow predecessor were completely absent. This leads to a significant or complete delay of seedlings, weak plant development, thinning and formation of a reduced number of productive stems for harvesting, and this indicator of the structure largely determines the value of the crop. By spring, the moisture content on background of fallow in 3 (43%) and semi-fallow in 4 years (57%) was lower than the average annual value. Of the 7 years in 3 severe summer-autumn droughts were combined with varying degrees of aridity in the spring-summer period. Yields of winter wheat averaged 3.71 t/ha on background of bare fallow and 1.85 t/ha on semi-fallow but in some years ranged from 2.74 to 5.68 and from 1.06 to 2.79 t/ha, or by 2.1–2.6 times, respectively. The size of a yield on background of fallow is by 2 times higher, than that on non-fallow; that testifies to expediency of application of fallow and of its stabilizing role in droughty conditions.

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